Synthetic turf systems, as alternatives to natural grass surfaces, are well known. They represent an improvement over natural grass in some respects, resisting wear and severe weather and typically requiring less maintenance. Prior art synthetic turf systems, sold under trademarks such as Field Turf, Sprint Turf, and Sportex, include a synthetic playing surface often coupled with infill materials.
Artificial grass is used as a covering for everything from landfills to playing fields to airport runways to landscaping to property subject to mudslides and landslides. Geosynthetically-lined slopes are also common. The liners are utilized as barriers and are produced from HDPE, PE, PP, PVC, and other polymers. For safety, improved performance and durability, and longevity, a number of limitations are placed upon the proper design of geosynthetically-lined structures. This is especially true when the liner is exposed to UV light or when natural vegetated cover materials are placed upon the liners.
The concept of using fibers as reinforcement likewise is not new. Fibers such as straw, hemp, asbestos, and synthetic fibers have been used as reinforcement, some since ancient times. In general, soils and concrete are considered to have low tensile characteristics. The addition of synthetic fibers in soils and concrete improves tensile characteristics of the soil or concrete, creating a composite system that benefits from the tensile elements of the fibers.
Geosynthetically-lined slopes have low friction with overlying materials. As a result, cover soils are subject to forces that destabilize the system. In fact, erosion is usually a major source of damage to man-made, as well as natural slopes. Erosion occurs by detachment and movement of soil particles due to impingement thereof by rain and/or surface runoff. When storms, high winds, or precipitation occur, seepage forces are introduced into the cover soils overlying the geomembranes; slope failures can occur. Loss of soil is calculated as a function of regional rainfall, a soil erodibility factor, length of the slope, angle of the slope, and cover management.
Such problems can be overcome by utilizing textured membranes and drainage geocomposites. The textured geomembranes increase the frictional characteristics between the interface between the geomembrane and drainage geocomposite. Drainage geocomposites synthetically replace natural drainage materials such as sand or stone. Drainage geocomposites evolved as a result of the limitations of natural drainage layers when placed above geosynthetically-lined slopes. These limitations included the ability to construct slopes at steep inclination angles.
Drainage geocomposites also have numerous limitations. For example, while drainage geocomposites may provide great speed at conveying fluids, they conversely lack any meaningful storage capacity as a result of their nominal thickness, typically less than 0.50 inches (1.27 cm). If a drainage geocomposite clogs or is improperly sized, the overlying soil becomes saturated. Saturated soils lose internal shear strength and cohesion and are subjected to seepage-induced forces resulting in massive slope failures. Drainage geocomposites are also susceptible to biological clogging. In fact, there are occasions when vegetative soil cover roots entirely clog geosynthetic drainage systems. Moreover, drainage geocomposites are susceptible to exposure to UV light. In fact, engineers often specify that the drainage geocomposite must be covered within 15 days or removed. As a result, requirements are imposed upon the speed at which a drainage geocomposite sloped structure may be installed. Litigation between contractors, engineers, subcontractors, and material suppliers has occurred based upon the construction sequence when utilizing drainage geocomposites.
Granular drainage layers are produced from uniform gradations of sand, stone, or even recycled materials, which may include boiler slag, glass, asphalt, or concrete. Quarries produce uniform gradations through myriad screening processes that sift out larger and smaller materials based upon the “diameter” (distance between extremities) of the materials. Since natural materials are granular, they are often more spherical than cubical. A quarry may actually even tumble natural material to decrease angularity and increase spherical properties. As a result, natural materials for drainage applications are specified based upon diameter and uniformity.
Spheres are circular and tough at tangential points. As a result, sand, stone, or recycled materials produced for uniform diameter achieve a degree of porosity when accumulated. The porosity is achieved because sand, stone, and these recycled materials resist compressive forces. By resisting compression the diameter is maintained and void areas are created. The porosity of the resulting void areas is highly desirable because it allows for the conveyance of fluid and gas.
Uniformly graded sand, stone, and recycled materials lack cohesion. The more cohesive a material, the less permeable the material. A lack of cohesiveness places significant limits on the slope inclination angle for natural or recycled drainage systems.
Despite the limitations of natural or recycled systems, they have significant benefits over synthetic systems in many instances. For example, natural or recycled systems are not subject to UV degradation. Additionally, natural or recycled systems require no protection, as they are not susceptible to puncturing. Often, natural or recycled materials may cost less expensive than do synthetic products.
U.S. Pat. No. 6,946,181, issued to Prevost for ARTIFICIAL GRASS FOR LANDSCAPING, discloses an artificial grass surface suitable for flat surfaces, such as bordering a runway of an airfield in order to reduce the presence of birds in the airfield. The artificial grass surface includes a pile fabric having a plurality of pile elements extending from a substantially impermeable layer mat and resembling grass. A water barrier is provided for preventing water from percolating to the compacted soil surface. Infilled particulate material is dispersed among the pile elements. A stabilizer is provided to resist dislodgment of the infilled particulate material at the edges of the runways by the thrust of jet engines and to keep the particulate material in the pile elements when the edges of the runways are vacuumed to remove silt.
U.S. Published Patent Application No. 2009/0094918 for TILE FOR SYNTHETIC GRASS SYSTEM on application by Stephen Murphy, et al. discloses a tile intended to be laid in the center of an area upon which the synthetic grass assembly will be installed.
U.S. Published Patent Application No. 2008/0216437 for TILE FOR A SYNTHETIC GRASS SYSTEM on application by Prevost, et al. also discloses a tile for a synthetic grass system. The tile has a top surface with a plurality of trusses and a bottom surface with a plurality of legs extending therefrom. The trusses intersect and form apertures. The top surface has a plurality of sections hingedly attached to adjacent sections with expansion members.
U.S. Published Patent Application No. 2008/0219770 for DRAINAGE SYSTEM FOR SYNTHETIC GRASS SYSTEM, METHOD OF INSTALLING A SYNTHETIC GRASS SYSTEM AND BUSINESS METHOD OF PROVIDING A SYNTHETIC GRASS SYSTEM on application by Prevost, et al. discloses a drainage system having a base having a center portion with a first depth and a perimeter channel with a second depth being greater than the first depth, a plurality of tiles above the base, and a synthetic grass above the plurality of tiles.
U.S. Pat. No. 7,128,497, issued to Daluise for HORIZONTALLY DRAINING ARTIFICAL TURF SYSTEM, discloses a horizontally draining artificial turf system comprising an impervious base at proper slope, an impermeable layer or drainage blanket over the base at a corresponding slope for guiding water horizontally, an artificial turf at top of the impermeable layer, and a perforated pipe near the lower edge of the base for receiving water for evacuation. Rainwater over the artificial turf first drains vertically onto the impermeable layer and then flows along the impermeable layer to reach the perforated pipe, without infiltrating into the base. Alternatively, a partially pervious drainage blanket is provided in lieu of the impermeable layer where the base is partially pervious. Backup rainwater runs off the drainage blanket horizontally after it saturates the soils of the base.
U.S. Pat. No. 7,682,105 issued to Ayers et al. for COVER SYSTEM FOR WASTE SITES AND ENVIRONMENTAL CLOSURES discloses a cover system comprising a synthetic grass and an impermeable geomembrane that can be applied without the use of heavy earthwork equipment as temporary or final cover to control odors, erosion, gas migration and contaminate migration. The cover system does not require the use of an extensive anchoring system to resist wind uplift or slope failure.
It is therefore an object of the present invention to provide a geosynthetic tufted drain barrier with low vertical permeability and high plane permeability or transmissivity, and to provide in-plane flow of liquid while constraining infill material.
It is also an object of the invention to provide means and methods for combining two or three layers of thermoplastic into such GTDB.
It is a further object of the invention to create a geosynthetic tufted drainage barrier structure that possesses low vertical permeability, but high plane permeability or transmissivity.
It is also an object of the invention to provide a GTDB that is laminated to a gas transmissive element, integrating an upper surface of synthetic turf to high transmissive geonet cores to permit the timely egress of undesirable fluids or gases.